Surgical removal of cataract is well known in the art. In cataract surgery, the content of the eye lens is completely removed leaving only the posterior lens capsule, in which an artificial lens may be subsequently installed. It is appreciated that one of the main risks in cataract surgery is a potential damage, e.g. rupture, of the lens capsule. In the past, it was common practice to "freeze" the entire lens using appropriate means and then, to remove the lens in its entirety via a large opening which is formed in the cornea, specifically, along the Cornea Limbus. This procedure resulted in damage to the lens capsule and to the vitreous body and is, therefore, no longer in use.
Presently, there are a number of known methods for removing cataract. FIG. 1 schematically illustrates a cross-sectional view of a human eye 10 during cataract surgery in accordance with one, commonly used, prior art method. A surgical instrument 12 and, optionally, a manipulation device 14, are inserted into eye lens 20 via cornea 16, a preferably dilated pupil 18 and an opening formed in the anterior capsule of lens 20. As is known in the art, lens 20 includes a core 28, known as the nucleus, which is formed of a relatively hard tissue. Core 28 is surrounded by a layer 26 of relatively soft, jell-like tissue, known as the cortex, which fills lens capsule 24.
The soft tissue in cortex layer 26 is typically removed gradually using a vacuum suction device and/or a "scooping" device (not shown in the drawings). To remove nucleus 28, the hard tissue is typically, first, broken into small fragments and/or dissolved using appropriate instruments and/or solutions and, then, removed gradually by suction and/or "scooping" as described above. Alternatively, the entire nucleus can be removed in one piece, however, this requires cutting a large opening in the cornea.
FIG. 1 illustrates one method of breaking nucleus 28 using directional ultrasonic transmission. According to this method, instrument 12 includes a device 25, generally known as a Phacoemulsifier (Hereinafter: "Phaco"), which transmits intense ultrasonic energy into nucleus 28. The crushing effect of the ultrasonic transmission of Phaco device 25 is typically enhanced by a stream of liquid 22 supplied from an external sleeve 23 of instrument 12, which liquid typically includes a dissolving agent. It is appreciated that, during surgery, a constant supply of liquids is generally required to compensate for escape of intraocular liquids and/or to assist in dissolving the content of lens 20. In the example shown in FIG. 1, the supply of liquid 22 via sleeve 3 is utilized both as a dissolving agent and as a compensatory liquid supply. However, it is appreciated that a separate liquid supply may additionally or alternatively be used.
Manipulation device 14 typically includes a thin, pointed instrument. For example, The thin pointed instrument can be a needle or a spatula, which provide partial counter-support to the operation of instrument 12 on nucleus 28. Such a device enables the surgeon to manipulate nucleus 28 by pushing it to a desired position and to temporarily support the nucleus at the desired position. However, it should be noted that the ability of the surgeon to manipulate and control nucleus 28 using device 14 is limited, due to various physical parameters. For example, the "angle of the attack" of device 14 on the traction between device 14 and the surface of nucleus 28 can be manipulated, using device 14, only by pushing and not by pulling.
Medical follow up studies reveal that the quality of the post-operative optical results depends on the size of the incision made during surgery, where smaller incisions are usually associated with better post-operative results.
An additional development favoring the reduction of the incision size is the availability of foldable artificial lenses which can be introduced into the eye and inserted into the capsula while folded inside a needle-like device of relatively small diameter.
Unfortunately, ultrasonic systems such as the Phacoemulsifier are relatively expensive. Moreover, during the operation, the surgeon cannot observe a clearly defined border of the crushing action of the Phaco device 25. Thus, the inexperienced surgeon might inadvertently damage the posterior capsule of the lens, resulting in poorer post-operative results.
Additionally, the geometry of the crushing zone around the tip of the Phaco device 25 is not constant and varies for different sonication intensities, while having no visible cue which the surgeon can use to determine the precise crushing range from the tip of the Phaco device 25.
Consequently, there is a steep learning curve for the surgeon, requiring a relatively long training period and resulting in lower quality of the post-operative results during the training period.
Furthermore, in certain cataract cases, the degree of hardening of the cataract nucleus 28 is such that the Phaco device 25 cannot crush it, thus, requiring the surgeon to broaden the small incision in order to remove the whole cataract nucleus.